Tissue repair system

ABSTRACT

A bone anchor includes an anchor body configured to be retained within bone. The anchor body includes a restrictor defining an opening having a first portion for permitting passage of a member therethrough, and a second portion restricting passage of the member therethrough. The member is movable between the first and second portions in a direction non-parallel to a direction of passage of the member through the opening. The restrictor includes an edge lining the opening oriented obliquely to a direction of passage of the member through the opening. The anchor body includes one or more resilient members with sharp, proximal edges for penetrating bone tissue.

BACKGROUND

[0001] This invention relates to tissue fixation devices and methods fortissue repair.

[0002] Fibrous tissues, such as ligaments and tendons, can detach frombone. The detachment can be repaired using sutures. It is known to fix afibrous tissue to bone by inserting a suture anchor through the fibroustissue and into the bone and knotting suture attached to the anchor totie down the fibrous tissue to the bone. Tying suture knots in minimallyinvasive surgical procedures commonly requires a skilled surgeon and/orspecialized equipment.

SUMMARY

[0003] According to one aspect of the invention, a bone anchor includesan anchor body configured to be retained within bone and to selectivelyrestrict movement of a flexible member coupled to the bone anchor suchthat after implantation, the flexible member can be moved through theanchor body in a first direction while, without the aid of an enlargedportion on the flexible member, e.g., a knot, movement in a second,opposite direction can be restricted.

[0004] Embodiments of this aspect of the invention may include one ormore of the following features. The bone anchor includes a restrictorconfigured to engage the flexible member to selectively restrictmovement of the flexible member. The restrictor is configured to engagethe flexible member at a substantially arbitrary position along a lengthof the flexible member. The anchor body defines an opening through whichthe flexible member can be moved, and the restrictor is configured toengage the flexible member to selectively restrict passage of theflexible member through the opening. The restrictor defines at least apart of the opening, for example, a narrower portion of the opening thananother portion of the opening.

[0005] In an illustrated embodiment, the restrictor includes a slopedsurface configured to compress the flexible member to permit passage ofthe flexible member through the opening, and opposing edges for engagingthe flexible member to limit passage of the flexible member through theopening.

[0006] The bone anchor includes a second restrictor configured to engagethe flexible member to selectively restrict passage of the flexiblemember through the opening. The restrictors are oppositely directed.

[0007] The anchor body includes a pair of legs, a bone-engaging ridgefor retaining the bone anchor in a bone hole, and a post about which theflexible member is positionable. The anchor body is a unitary body.

[0008] According to another aspect of the invention, a tissue repairsystem includes a first anchor body including a member that engages boneto retain the anchor within the bone and a second anchor body includinga member that engages bone to retain the anchor within the bone. Theanchor bodies each define an opening for receiving suture and arestrictor forming a one-way passage through the opening. The anchorbodies are coupled by a suture extending through the one-way passages.

[0009] According to another aspect of the invention, a bone anchorincludes an anchor body configured to be retained within bone and toreceive a flexible member such that after implantation of the anchorbody within bone, the flexible member can be moved through the anchorbody while, without the aid of an enlarged portion on the flexiblemember, subsequent movement of the anchor body can be restricted.

[0010] According to another aspect of the invention, a tissue repairsystem includes a flexible member, and first and second bone anchorscoupled together by the flexible member. Each bone anchor includes ananchor body configured to be retained within bone. At least one of thebone anchors is configured to receive the flexible member such that theflexible member can be pulled to shorten a length of the flexible memberbetween the bone anchors, while, without the aid of an enlarged portionon the flexible member, subsequent lengthening of the flexible memberbetween the bone anchors can be restricted.

[0011] According to another aspect of the invention, a bone anchorincludes an anchor body configured to be retained within bone. Theanchor body defines a one-way passage configured to pass a suture in afirst direction and restrict passage of the suture in a second directionopposite the first direction.

[0012] According to another aspect of the invention, a bone anchorincludes an anchor body configured to be retained within bone. Theanchor body includes a restrictor defining an opening having a firstportion for permitting passage of a member therethrough, and a secondportion restricting passage of the member therethrough without the aidof an enlarged portion on the member.

[0013] According to another aspect of the invention, a method includesplacing an anchor in bone, moving a flexible member through the anchorin a first direction, and restricting movement of the flexible memberthrough the anchor in a second, opposite direction.

[0014] Embodiments of this aspect of the invention may include placing asecond anchor in bone. The second anchor is coupled to the first anchorby the flexible member. The step of moving the flexible member in thefirst direction shortens a length of the flexible member between theanchors.

[0015] According to another aspect of the invention, a bone anchorincludes an anchor body configured to be retained within bone. Theanchor body includes a restrictor defining an opening having a firstportion for permitting passage of a member therethrough, and a secondportion restricting passage of the member therethrough. The member ismovable between the first and second portions in a directionnon-parallel to a direction of passage of the member through theopening.

[0016] Embodiments of this aspect of the invention may include one ormore of the following features.

[0017] The restrictor includes one or more edges lining a wall of theopening. The edge is oriented obliquely to a direction of passage of themember through the opening. Some of the edges are oriented at the sameoblique angle relative to the direction of passage of the member throughthe opening, and some of the edges are oriented parallel to each other.

[0018] A dimension of the second portion is narrower than a diameter ofthe member. The opening is triangular in shape. The anchor is configuredsuch that the member is movable between the first and second portionssubstantially perpendicularly to a direction of passage of the memberthrough the opening.

[0019] In an illustrated embodiment, the anchor body includes a tissuepenetrating tip, and a central body member with a driver coupling. Theanchor body includes one or more resilient members with sharp, proximaledges for penetrating bone tissue. The anchor body is a unitary body.

[0020] According to another aspect of the invention, a tissue repairsystem includes a first bone anchor with an anchor body configured to beretained within bone, and a second bone anchor with an anchor bodyconfigured to be retained within bone. A flexible member couples thefirst and second bone anchors. At least one of the first and secondanchor bodies includes a restrictor defining an opening having a firstportion for passage of the flexible member therethrough, and a secondportion limiting passage of the flexible member therethrough. Theflexible member is movable between the first and second portions in adirection non-parallel to a direction of passage of the member throughthe opening.

[0021] According to another aspect of the invention, a bone anchorincludes an anchor body configured to be retained within bone. Theanchor body includes a restrictor defining an opening for passage of amember therethrough. The restrictor includes an edge lining a wall ofthe opening oriented such that upon movement of the member through theopening in a first direction, the member is also moved non-parallel tothe first direction.

[0022] Embodiments of this aspect of the invention may include the edgebeing oriented such that upon movement of the member through the openingin a second direction opposite the first direction, the member is alsomoved non-parallel to the second direction. The restrictor includes asecond edge lining a wall of the opening. The second edge is orientedsuch that upon movement of the member through the opening in a seconddirection opposite the first direction, the member is also movednon-parallel to the second direction.

[0023] According to another aspect of the invention, a method includesplacing an anchor in bone and moving a member between first and secondportions of an opening in the anchor in a direction non-parallel to adirection of passage of the member through the opening.

[0024] Embodiments of this aspect of the invention may include one ormore of the following features.

[0025] The method includes engaging the member with an edge lining theopening. Moving the member to the second portion includes moving themember in a direction substantially perpendicular to a direction movedby the member through the first portion. A second anchor coupled to thefirst anchor by the member is placed in the bone.

[0026] Advantages of the invention may include permitting surgeons withvarying skill levels to straightforwardly reattach tissue to bone inopen or closed surgical procedures. The surgeon is able to fix a fibroustissue to bone using an appropriate tension simply by pulling a suturereceived by the bone anchor in a first direction. Since the bone anchorsof the present invention limit subsequent movement of the suture in theopposite direction, the surgeon is able to easily select the appropriatetension.

[0027] The details of one or more embodiments of the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0028]FIG. 1 is a diagrammatic illustration of a system for reattachingfibrous tissue to bone;

[0029]FIG. 2A is a perspective view of a bone anchor;

[0030]FIGS. 2B and 2C are side views of the bone anchor of FIG. 2A;

[0031]FIG. 2D is a cross-sectional view of the bone anchor of FIG. 2Ataken along lines 2D-2D of FIGS. 2B and 2C;

[0032]FIGS. 2E and 2F are respectively top and bottom views of the boneanchor of FIG. 2A;

[0033]FIG. 3A is a perspective view of an alternative embodiment of abone anchor;

[0034]FIGS. 3B and 3C are side views of the bone anchor of FIG. 3A;

[0035]FIG. 3D is a cross-sectional view of the bone anchor of FIG. 3Ataken along lines 3D-3D of FIGS. 3B and 3C;

[0036]FIGS. 3E and 3F are respectively top and bottom views of the ofthe bone anchor of FIG. 3A;

[0037]FIG. 3G is another perspective view of the bone anchor of FIG. 3A;

[0038]FIG. 4A is a perspective view of another alternative embodiment ofa bone anchor;

[0039]FIG. 4B is a side view of the bone anchor of FIG. 4A;

[0040]FIG. 4C is a cross-sectional side view of the bone anchor of FIG.4A taken along lines 4C-4C of FIG. 4B;

[0041]FIG. 4D is another side view of the bone anchor of FIG. 4A;

[0042]FIG. 4E is a cross-sectional side view of the bone anchor of FIG.4A taken along lines 4E-4E of FIG. 4D;

[0043]FIG. 4F is another side view of the bone anchor of FIG. 4A;

[0044]FIG. 4G is a cross-sectional side view of the bone anchor of FIG.4A taken along lines 4G-4G of FIG. 4F;

[0045]FIG. 5 is a cross-sectional side view of the bone anchor of FIG.4A shown with a suture coupled thereto; and

[0046]FIG. 6 illustrates the bone anchor of FIG. 4A in use.

DETAILED DESCRIPTION

[0047] Referring to FIG. 1, a tissue repair system 8 for attaching softtissue 22, e.g., tendon, ligament, or cartilage, to bone 20 includes aflexible member, e.g., suture 10, coupled to first and second boneanchors 16, 18. Suture 10 includes contiguous suture portions 10 a, 10 band 10 c. In use, bone anchors 16, 18 are located within holes 11, 13 inbone 20, with first suture portion 10 a extending from bone anchor 16through a hole 30 in tissue 22 to a first suture end 6, second sutureportion 10 b spanning between bone anchors 16, 18 and lying along anouter surface 23 of tissue 22, and third suture portion 10 c extendingfrom bone anchor 18 through a hole 32 in tissue 22 to a second sutureend 7.

[0048] Bone anchors 16, 18 each include a first engagement system 17through which suture 10 is threaded. After implantation in bone 20, thephysician pulls on one or both of the ends 6, 7 of suture 10 to shortenthe length of suture portion 10 b, thus securing tissue 22 against bone20. Engagement systems 17, discussed further below, couple suture 10 tobone anchors 16, 18 and limit possible loosening of tissue repair system8 following tissue securement.

[0049] Referring to FIG. 2A, bone anchors 16, 18 each have a flat,distal tip 15 and a pair of legs 31, 33 extending proximally from tip 15to a proximal end 26. Legs 31, 33 are generally part-circular in shape(FIG. 2E) with a region of increased outer diameter defined by a seriesof radial ridges (here three ridges 19 a, 19 b, 19 c shown) that engagebone tissue to resist the withdrawal of the anchor from the bone hole.Each ridge 19 a, 19 b, 19 c has a sloped distal face 2, a proximal face3 that is substantially normal to the long axis, X, of bone anchors 16,18, and a bone engaging edge 4 (FIG. 2B) defined at the intersection offaces 2 and 3.

[0050] Engagement system 17 includes a pair of restrictor cleats 40, 50at the proximal end 26 of legs 31, 33. Legs 31, 33 have inner walls 31a, 33 a (FIG. 2B), respectively, that define a slot opening 35therebetween extending from proximal end 26 to a distal chamber 60.Located within chamber 60 is a winding post 62. The open sides of slotopening 35 provide easy access to winding post 62 to aid in threadingsuture 10 around post 62, though the sides need not be open. Cleats 40,50 act to selectively restrict passage of suture 10 through opening 35,as described further below.

[0051] As shown in FIG. 2D, winding post 62 extends into chamber 60 froma wall 61 at a back side 16 b of anchor 16. Winding post 62 and wall 61are tapered inwardly toward distal tip 15 to provide a smooth, tapereddistal portion. Chamber 60 circumscribes winding post 62, and is open ata front side 16 a of the bone anchor to aid in threading suture 10through anchor 16. Suture 10 is threaded through anchor 16 such that thesuture passes through cleat 50 and opening 35, into interior chamber 60and around winding post 62, then through opening 35 and cleat 40.Winding post 62 contacts and retains suture 10 within interior chamber60, and is of sufficient mechanical strength to withstand tensionapplied to suture 10.

[0052] Referring to FIGS. 2B and 2C, cleat 40 is formed by an opposingpair of protrusions 40 a having proximal faces 42, 44 that define anarrower portion 35 a of channel 35 therebetween, and distal faces 46,48 that define a wider, sloped portion 35 b of channel 35 therebetween.Cleat 50 is oriented opposite of cleat 40 with an opposing pair ofprotrusions 50 a having distal faces 52, 54 that define a narrowerportion 35 c of channel 35 therebetween, and proximal faces 56, 58 thatdefine a wider, sloped portion 35 d of channel 35 therebetween. Proximalfaces 42, 44 have opposing edges 43, 45 (defined by the proximal cornersof faces 42, 44), and distal faces 52, 54 have opposing edges 53, 55(defined by the distal corners of faces 52, 54). Each opposing pair ofedges 43, 45 and 53, 55 is separated by a separation distance that issubstantially equal to or smaller than the diameter of suture 10.

[0053] Movement of suture 10 through sloped portions 35 b, 35 d ofcleats 40, 50 acts to compress the suture such that the suture can passthrough narrower portions 35 a, 35 c, respectively, when pulled in thedirection of arrow 70 (FIG. 1). However, loosening of suture 10 (passageof suture 10 through the cleats in a direction opposite arrow 70) islimited by opposing edges 43, 45 and 53, 55 catching on uncompressedsuture 10 such that the suture does not pass through the cleats. Ineffect, cleats 40, 50 form a one-way passage.

[0054] Referring again to FIG. 1, suture 10 is threaded through anchors16 and 18 such that from suture end 6, suture portion 10 a passesthrough cleat 40 in anchor 16 to post 62, suture portion 10 b extendsfrom post 62 through cleat 50 in anchor 16, then through cleat 50 inanchor 18, to post 62, and suture portion 10 c extends from post 62through cleat 40 in anchor 18 to suture end 7. This permits the sutureto pass through the cleats (with the sloped portions of the cleatscompressing the suture such that the suture can pass through the narrowportions of the cleats) when ends 6, 7 are pulled in the directions ofarrows 70, 72, respectively, to shorten suture length 10 b, but resistspassage through the cleats (by the opposing edges of the cleats catchingon uncompressed suture) when a load tending to lengthen suture length 10b is placed on the suture.

[0055] In use, the operator implants first and second bone anchors 16,18 into, e.g., a predrilled hole in bone 20 through tissue 22 (and anoverlaying cartilage layer, if present) by, e.g., applying a compressiveor torsional load to members 16, 18 as appropriate. The operator thendraws one or both ends 6, 7 of suture portions 10 a, 10 c in thedirection of arrows 70, 72 to shorten the length of suture portion 10 bbetween first and second bone anchors 16, 18. Suture portion 10 b drawstissue 22 toward bone 20. The anchors can be supplied to the operatorwith suture 10 prethreaded to through anchors 16, 18, or the operatorcan thread suture 10 through the anchors.

[0056] When suture portion 10 b is sufficiently taut, the operatorreleases and/or cuts the free ends of the suture extending from the softtissue. Although, during healing, a patient may apply forces that tendto draw tissue 22 away from bone 20, engagement systems 17 resist thelengthening of suture portion 10 b. In particular, cleats 40, 50restrict passage of the suture portion 10 c in the direction opposite toarrow 72 and suture portion 10 a in the direction opposite to arrow 70.Moreover, cleats 40, 50 engage and restrict the passage of suture 10 ata substantially arbitrary position along the length of suture 10. Inother words, there is no need, e.g., to clamp suture 10 with anothermember, or have an enlarged portion such as a knot in suture 10 torestrict the passage of suture 10 through the cleats. Cleats 40, 50 thusselectively restricts movement of suture 10 by allowing the passage ofsuture 10 through the cleats in a first direction while subsequentpassage of suture 10 in a second, opposite direction is restricted.

[0057] Other embodiments are within the scope of the following claims.For example, referring to FIGS. 3A-3F, particularly to FIGS. 3A and 3D,rather than a post 62 extending from a side wall, an alternate boneanchor 67 includes a central member 120 with side posts 112 a, 112 blocated in chamber 60. Side posts 112 a, 112 b taper inwardly to providea smooth, tapered distal portion. The outer dimension of side posts 112a, 112 b is less than the diameter of chamber 60 such that channels 110a, 110 b, respectively, are formed about side posts 112 a, 112 b, whilethe outer diameter of central member 120 is equal to the diameter ofchamber 60. Posts 112 a, 112 b and central member 120 defines atransverse passage 87 (FIG. 3G) for passage of suture from channel 110 ato 110 b. Side posts 112 a, 112 b have a half-moon shape such that acircular suture passage 87 is formed. Other side posts shapes arepossible. Suture 10 passes through cleat 40 to channel 35, to channel110 a and around post 112 a to passage 87, through passage 87, tochannel 110 b around post 112 b to channel 35, and through cleat 50.

[0058] Referring to FIG. 4A, a bone anchor 200 includes a central member230, a distal tip 215, and a series of proximally extending, radialwings 219 a, 219 b, 219 c, 219 d surrounding central member 230. Centralmember 230 includes a restrictor in the form of a suture guiding throughchannel 235 that selectively restricts passage of suture therethrough,as described below. Distal tip 215 is conical in shape and has a tissuepenetrating point 215 a. Radial wings 219 a, 219 b, 219 c, 219 d arejoined at a distal end 221 of the wings to a proximal end 216 of distaltip 215, and resiliently flare outwardly from central member 230 in aproximal direction. Each wing has a sharp proximal edge 219 a′, 219 b′,219 c′, 219 d′ for digging into bone tissue to resist withdrawal ofanchor 200 from the bone. Wings 219 a, 219 b, 219 c, 219 d are inwardlydeformable toward central member 230 in response to radial compression,such as during insertion into a generally circular opening or hole inbone formed, e.g., by insertion of distal tip 215 into the bone. Centralmember 230 defines a proximal opening 240 for receiving a drive tool,not shown, for pounding anchor 200 into bone.

[0059] Referring to FIGS. 4B-4G, suture guiding channel 235 has agenerally triangular cross-section with a proximal apex 225, a distalbase face 227, and a pair of side faces 228 a, 228 b. Side faces 228 a,228 b converge proximally forming a distal portion 237 of channel 235that is wider than the diameter of the suture, such that the suture canpass freely therethrough, and a proximal restricting portion 239 ofchannel 235 that is narrower than the suture diameter to restrictpassage of the suture therethrough. Referring particularly to FIGS. 4Cand 4E, base face 227 follows an arcuate path through central member230, as does apex 225 at the intersection of side faces 228 a, 228 b. Asillustrated, the radius of curvature of the path of apex 225 thoughcentral member 230 is approximately equal to one half the diameter ofcentral member 230. The curvature of apex 225 presents an atraumaticsurface for the suture to rest against when pulled taught, as discussedbelow.

[0060] Side faces 228 a, 228 b are each lined by a series of grooves 250a, 250 b, 250 c, 250 d. Though four grooves are shown, one or moregrooves can be employed. As illustrated, grooves 250 a, 250 b, 250 c,250 d are relatively uniformly oriented with respect to base face 237and apex 225 of channel 235 such that the grooves have the same obliqueangle relative to a suture passing through channel 235, as shown in FIG.5. Each groove 250 a-250 d has a first edge 253 a-253 d, respectively,and a second edge 254 a-254 d, respectively, oriented generally parallelto the respective first edge and obliquely relative to the passage ofsuture 10 through channel 235.

[0061] Edges 253 a-253 d and 254 a-254 d, along with the shape ofchannel 235, act to permit suture to be pulled in a first directionwhile limiting movement of the suture in a second opposite direction.Referring to FIGS. 4C and 5A, when suture 10 is pulled in the directionof arrow 11, contact of suture 10 with edges 253 a-253 d pushes suture10 in a direction non-parallel to the direction of travel of suture 10through channel 235. The action of edges 253 a-253 d upon suture 10moves suture 10 toward base face 227 into distal channel portion 237,allowing suture 10 to pass through channel 235. When suture 10 is pulledin the direction of arrow 12, contact of suture 10 with edges 254 a-254d pushes suture 10 in a direction non-parallel to the direction oftravel of suture 10 through channel 235. The action of edges 254 a-254 dupon suture 10 moves suture 10 toward apex 225 into proximal restrictingportion 239, which acts to compress suture 10 and restrict passage ofsuture 10 through channel 235.

[0062] Referring to FIG. 6, one or more anchors 200 with suture 10prethreaded through channel 235 can be deployed through tissue 300 intobone 302. During deployment, wings 219 a-219 d are initially compressedas they pass through corticol bone, and then expand into the cancellousbone to retain anchors 200 in the bone. By moving suture 10 in thedirection of arrow 11, the length of suture between two anchors 200 canbe shortened, pulling suture 10 taught, while any tendency of the sutureto loosen is limited by movement of suture 10 into proximal restrictingportion 239 of channel 235 in response to tension applied to suture 10in the direction of arrow 12. Suture guiding channel 235 and edges 253a-253 d and 254 a-254 d in anchor 200 thus selectively restrictsmovement of suture 10 by allowing the passage of suture 10 throughportion 237 of channel 235 in a first direction, while restrictingsubsequent passage of suture 10 in a second, opposite direction byengaging suture 10 in apex 225 at a substantially arbitrary positionalong the length of the suture 10, without the need for an enlargedportion such as a knot in the suture.

[0063] Further alternative embodiments are within the scope of theclaims. For example, a single bone anchor can be used, or the suture canbe fixed to a first anchor and coupled to a second anchor configured toselectively restrict movement of the suture, as described above. A boneanchor can include only one or more than two cleats. Suture 10 cancouple more than two bone anchors in a tissue repair system. Any of anumber of different geometries and/or types of bone anchors as describedin, e.g., U.S. Pat. Nos.: 5,224,946 to Hayhurst et al., 5,236,455 toHayhurst et al., and 5,100,417 to Cerier et al., the contents of all ofwhich are incorporated herein by reference in their entirety, can bemodified to include means according to the invention for selectivelyrestricting passage of suture. Winding posts and side posts can bereplaced by any of a number of different structures that contact thesuture and retain it in the bone anchor, including eyelets, bosses, etc.Edges can be formed by ridges protruding from the side walls.

What is claimed is:
 1. A bone anchor comprising: an anchor bodyconfigured to be retained within bone, the anchor body including arestrictor defining an opening having a first portion for permittingpassage of a member therethrough, and a second portion restrictingpassage of the member therethrough, the member being movable between thefirst and second portions in a direction non-parallel to a direction ofpassage of the member through the opening.
 2. The bone anchor of claim 1wherein the restrictor includes an edge lining a wall of the opening. 3.The bone anchor of claim 2 wherein the edge is oriented obliquely to adirection of passage of the member through the opening.
 4. The boneanchor of claim 2 wherein the restrictor includes multiple edges liningthe wall of the opening.
 5. The bone anchor of claim 4 wherein at leastsome of the edges are oriented at the same oblique angle relative to thedirection of passage of the member through the opening.
 6. The boneanchor of claim 4 wherein at least some of the edges are orientedparallel to each other.
 7. The bone anchor of claim 1 wherein adimension of the second portion is narrower than a diameter of themember.
 8. The bone anchor of claim 1 wherein the opening is triangularin shape.
 9. The bone anchor of claim 1 configured such that the memberis movable between the first and second portions substantiallyperpendicularly to a direction of passage of the member through theopening.
 10. The bone anchor of claim 1 wherein the anchor body includesa tissue penetrating tip.
 11. The bone anchor of claim 1 wherein theanchor body includes a central body member.
 12. The bone anchor of claim10 wherein the central body includes a driver coupling.
 13. The boneanchor of claim 1 wherein the anchor body includes a resilient memberfor engaging bone tissue.
 14. The bone anchor of claim 13 wherein theresilient member has a sharp, proximal edge for penetrating bone tissue.15. The bone anchor of claim 1 wherein the anchor body includes multipleresilient members.
 16. The bone anchor of claim 1 wherein the anchorbody comprises a unitary body.
 17. A tissue repair system comprising: afirst bone anchor including a first anchor body configured to beretained within bone, a second bone anchor including a second anchorbody configured to be retained within bone, and a flexible membercoupling the first and second bone anchors, at least one of the firstand second anchor bodies includes a restrictor defining an openinghaving a first portion for passage of the flexible member therethrough,and a second portion limiting passage of the flexible membertherethrough, the flexible member being movable between the first andsecond portions in a direction non-parallel to a direction of passage ofthe member through the opening.
 18. A bone anchor, comprising: an anchorbody configured to be retained within bone, the anchor body including arestrictor defining an opening for passage of a member therethrough, therestrictor including an edge lining a wall of the opening oriented suchthat upon movement of the member through the opening in a firstdirection, the member is also moved non-parallel to the first direction.19. The bone anchor of claim 18 wherein the edge is oriented such thatupon movement of the member through the opening in a second directionopposite the first direction, the member is also moved non-parallel tothe second direction.
 20. The bone anchor of claim 18 wherein therestrictor includes a second edge lining the wall of the opening, thesecond edge being oriented such that upon movement of the member throughthe opening in a second direction opposite the first direction, themember is also moved non-parallel to the second direction.
 21. A methodcomprising: placing an anchor in bone, the anchor body including arestrictor defining an opening having a first portion for permittingpassage of a member therethrough, and a second portion restrictingpassage of the member therethrough, moving the member between the firstand second portions in a direction non-parallel to a direction ofpassage of the member through the opening.
 22. The method of claim 21further comprising engaging the member with an edge lining a wall of theopening.
 23. The method of claim 21 wherein moving the member to thesecond portion comprises moving the member in a direction substantiallyperpendicular to a direction moved by the member through the firstportion.
 24. The method of claim 21 further comprising placing a secondanchor in bone, the second anchor being coupled to the first anchor bythe member.